Olefin isomerization catalyst

ABSTRACT

Double bond isomerization of olefins utilizing a catalyst comprising nickel and sulfur on a porous carrier; the catalyst being prepared by forming an initial composite of the nickel with the carrier material, sulfiding the initial composite to provide a sulfur/nickel atomic ratio of at least about 0.9 in the sulfided composite, and then stripping sufficient sulfur from the sulfided composite with hydrogen to provide a final isomerization catalyst composition having a sulfur/nickel atomic ratio of less than about 0.9 and more than about 0.55.

United States Patent [191 Germanas et al.

[ June 28, 1974 OLEFIN ISOMERIZATION CATALYST [75] Inventors: DaliaGermanas, Des Plaines; Ernest L. Pollitzer, Skokie, both of Ill.

[73] Assignee: Universal Oil Products Company, Des Plaines, Ill.

[22] Filed:

Primary Examiner-Patrick P. Garvin Attorney, Agent, or Firm-James R.Hoatson, Jr.; Thomas K. McBride; William H. Page, ll

[5 7] ABSTRACT Double bond isomerization of olefins utilizing a catalystcomprising nickel and sulfur on a porous carrier; the catalyst beingprepared by forming an initial composite of the nickel with the carriermaterial, sulfiding the initial composite to provide a sulfur/nickelatomic ratio of at least about 0.9 in the sulfided composite, and thenstripping sufficient sulfur from the sulfided composite with hydrogen toprovide a final isomerization catalyst composition having asulfur/nickel atomic ratio of less than about 0.9 and more than about0.55.

6 Claims, N0 Drawings 1 OLEFIN ISOMERIZATION CATALYST BACKGROUND OFINVENTION This invention concerns a process for isomerizing the doublebond in olefins to provide different, isomeric olefins.

This invention also relates to a novel catalyst composition useful as acatalyst for olefin double bond isomerization.

This invention further relates to a process for isomerizing the doublebond of an olefin without undesirable polymerization of hydrogenation ofthe olefin.

A number of catalysts capable of isomerizing the double bond of anolefin are known in the art. Such catalysts are capable, for example, ofconverting butene-l to butene-2, the 2-isomer being more valuablecommercially than the l-isomer. Many of the previously known catalystshave been found deficient in various ways, especially where they areemployed under commercial operating conditions.

One serious drawback found in many previously disclosed olefinisomerization catalysts is their lack of selectivity. In an olefinisomerization operation, the catalyst must be selective for the doublebond shift. For example, when it is desired to convert butene-l tobutene-Z, a more valuable chemical, the catalyst must be capable ofselectively catalyzing this double bond shift without converting thebutene-l to other compounds such as polybutenes, isobutylene, n-butane,or lower molecular weight hydrocarbons. In this case, selectivity refersto the ability of the catalyst to isomerize the double bond in thereactant compound without causing the reactant compound to polymerize,crack, or hydrogenate, or causing carbon chain rearrangement in thereactant compound.

In order for a double bond shift catalyst to be commercially acceptable,it must be active for the desired double bond shift at temperatures atwhich equilibrium between double bond isomers favors conversion to thedesired double bond isomer, while remaining inert with respect to othercompounds commingled with the reactant compound during the isomerizationreaction. The olefins which it is desired to isomerize in commercialoperations are generally available only in admixture with otherhydrocarbons. For example, all economically feasible sources can providebutene-l only in admixture with isobutylene. Because of the very similarboiling points of butene-l and isobutylene, it is completely impracticalto attempt to separate butene-l from isobutylene by fractionation.Butene-2, on the other hand, can economically be separated from butene-land isobutylene by fractionation. Thus, in commercial operation forisomerizing butene-l to provide butene-Z, the butene-l feed to theisomerization operation always contains a significant amount ofisobutylene. In order to utilize an olefin isomerization catalyst insuch an isomerization operation, the catalyst must be capable ofcatalyzing the conversion of butene-l into butene-2 at temperatureswhere butene-2 is favored by equilibrium, while remaining inert to theisobutylene. It is well known in the art that certain olefins,particularly isobutylene, polymerize very readily to fomi high molecularweight. hydrocarbons. Heretofore, it has been difficult to convertbutene-l into butene-2 in the presence of isobutylene without causingpolymerization of the isobutylene. Except for diisobutylene, thepolymers of isobutylene are of very little economic utility, whileisobutylene itself is valuable as, for example, a feed stock for use inan isoparaffin-olefin alkylation operation. It is therefore undesirableto polymerize the isobutylene during an operation to isomerize thebutene-l to provide butene-2.

Because of the relative lack of successin using previously knowncatalysts to provide a stable operation while remaining active andselective at temperatures favorable to high olefin conversion rates,previous attempts to provide an olefin double bond isomerization processhave generally not been completely successful. The process of thepresent invention overcomes selectivity and stability difficulties andprovides a practical and desirable method for shifting the double bondin olefinic hydrocarbons.

SUMMARY OF INVENTION It is an object of the present invention to providea catalyst suitable for double bond isomerization of olefinichydrocarbons.

Another object of the present invention is to provide a process fordouble bond isomerization of olefins.

Another object of the present invention is to provide an olefinisomerization catalyst which is selective for double bond isomerizationof olefins.

Another object of this invention is to provide an olefin isomerizationcatalyst which possesses high activity for double bond isomerization.

A further object of this invention is to provide an olefin double bondisomerization catalyst which possesses stability of performance at highrates of conversion.

Another object of the present invention is to provide an olefinisomerization catalyst capable of converting butene-l to providebutene-2 in the presence of isobutylene without causing polymerizationof the isobutylene, and without rapid deactivation of the catalyst.

Another object of the present invention is to provide a process forisomerizing butene-l, while in admixture with isobutylene, to providebutene-Z, without polymerizing the isobutylene.

Another object of the present invention is to provide an olefinisomerization process and catalyst capable of isomerizing linear olefinsby double bond shift without hydrogenating the linear olefins to linearparaffins.

Therefore, in an embodiment, the present invention relates to an olefinisomerization catalyst comprising a combination of a sulfur componentand a catalytically effective amount of a nickel component with a porouscarrier material, the catalyst containing less than about 0.9 and morethan about 0.55 mole of sulfur per mole of the nickel component,calculated as the elemental metal, and the catalyst being prepared bythe steps of: forming an initial composite of the nickel component andthe carrier material, the nickel component being present in the initialcomposite in a form selected from the elemental metal or the oxide;sulfiding the initial composite by contacting same with a sulfideyielding compound at sulfiding conditions to provide a sulfidedcomposite containing at least about 0.9 mole of sulfur per mole of thenickel component in the sulfided composite; and, stripping sulfur fromthe resulting sulfided composite with a hydrogen-containing gas atstripping conditions to provide the olefin isomerization catalyst,sufficient sulfur being stripped from the sulfided composite to providea sulfur content in the catalyst of less than about 0.9 and more thanabout 0.55 mole of sulfur per mole of the nickel component in thecatalyst.

In another embodiment, the present invention relates to a process forisomerizing an isomerizable olefin which comprises contacting theolefin, at olefin isomerization conditions, with an olefin isomerizationcatalyst comprising a combination of a sulfur component and acatalytically effective amount of a nickel component with a porouscarrier material, the catalyst containing less than about 0.9 and morethan about 0.55 mole of sulfur per mole of the nickel component,calculated as the elemental metal, and the catalyst being prepared bythe steps of: forming an initial composite of the nickel component andthe carrier material, the nickel component being present in the initialcomposite in a form selected from the elemental metal or the oxide;sulfiding the initial composite by contacting same with a sulfideyielding compound at sulfiding conditions to provide a sulfidedcomposite containing at least about 0.9 mole of sulfur per mole of thenickel component in the sulfided composite; and stripping sulfur fromthe resulting sulfided composite with a hydrogen-containing gas atstripping conditions to provide the olefin isomerization catalyst,sufficient sulfur being stripped from the sulfided composite to providea sulfur content in the catalyst of less than about 0.9 and more thanabout 0.55 mole of sulfur per mole of the nickel component in thecatalyst.

By employing the catalyst and processing condition more fully describedhereinafter, isomerizable olefins can be converted to different,isomeric olefins with a very high yield of the desired isomeric olefins.The catalyst of the present invention exhibits none of the undesirablecharacteristics of many catalysts, such as insta' bility and lack ofselectivity. Thus, isomerizable olefins may be converted to different,isomeric olefins in the present process without cracking, hydrogenationor polymerization of the reactant olefin, without rapid deactivation ofthe catalyst, and without adverse effects on any other hydrocarbonspresent during the isomerization operation. For example, butene-l may beisomerized, while in admixture with isobutylene, to provide essentiallyequilibrium conversion of the butene-l into butene-2, without theoccurence of any adverse side reactions such as polymerization ofisobutylene, hydrogenation of butene-l, or skeletal isomerization of anyhydrocarbons in the feed stock. Moreover, the foregoing is accomplishedunder very moderate conditions of operation, thus providing savings inthe capital and utilities requirements in commercial embodiments of theprocess.

DETAILED DESCRIPTION OF INVENTION One essential feature of the presentinvention is a catalyst composition containing nickel and sulfur on aporous carrier material, or support, which exhibits surprising activity,selectivity and stability when employed as a catalyst for double bondisomerization of olefins. The method of preparation of the compositionis a critical factor in insuring that the composition possesses thedesired high isomerization activity while, at the same time, exhibitingboth excellent stability over long periods of use and surprisinginertness to diluent hydrocarbons, even in the presence of very easilypolymerizable diluent materials such as isobutylene, as well as lack ofhydrogenation of the reactant olefin to a paraffin.

The first step in the preparation of the catalytic composition of thepresent invention is the formation of an initial composite of the nickelcomponent with the porous carrier material. The nickel component in theinitial composite is in the form of reduced nickel, i.e., the elementalmetal, or else is in the form of nickel oxide. Either the oxide or theelemental metal may be used with good results. The amount of nickel inthe initial composite, calculated on the basis of the elemental metal,is between about 5 wt. percent and about 80 wt. percent of the totalweight of the initial composite, with a preferred range of nickelcontent being about 10 wt. percent to about wt. percent of the totalinitial composite.

The porous carrier material employed in the present catalyst compositionis relatively inert and refractory under the condition employed in theisomerization operation. A variety of suitable support materials may beemployed in the catalyst. For example, any of the following may beutilized to provide the porous carrier material within the scope of thisinvention: activated carbon, coke or charcoal; silica, silica gel,synthetic or naturally occurring silicate such as kieselguhr, attapulgusclay, china clay, fullers earth, kaoline, etc., and refractory inorganicoxides such as alumina, titania, zirconia, chromia, zinc oxide,magnesia, thoria, boria, etc., as well as mixtures and combinations ofthe above. The preferred porous carrier materials are refractoryinorganic oxides, especially silica, alumina, and kieselguhr.

The initial composite of the nickel component and the carrier materialmay be prepared in any suitable conventional manner. For example, thecarrier may be formed into spheres or pellets or extruded, pilled, etc.The nickel component is then impregnated thereon by contacting thecarrier with a solution of a soluble and heat-decomposable nickelcompound and evaporating the solute, leaving a nickel compound depositedon the carrier. The composite is then heated to decompose the nickelcompound, the nickel being converted into the oxide or elemental metal,depending upon the heating atmosphere. Another suitable method forpreparing the initial composite of the nickel component and the porouscarrier material is by co-extrusion. In this operation, an aqueousrefractory inorganic oxide sol is ad mixed with a water soluble nickelcompound such as nickel nitrate, nickel sulfate or nickel chloride. Theaqueous mixture is then combined with an aqueous alkaline solution of,for example, ammonium hydroxide, ammonium carbonate, or the like, toprecipitate a mass of finely-divided particles. The mass of particlesproduced is then partially dried and compressed or extruded byconventional means to fonn pills, pellets, etc. The particles are heatedand dried to convert the nickel to the elemental metal or oxide. Variousother known methods for forming the initial composite of nickelcomponent and carrier are also suitable, including, for example, forminga mixture of dry, finelydivided particles of the porous carrier withfinely-divided particles of nickel or a nickel compound, extruding orcompressing the mixture into pills or pellets, and heating, if necessaryto decompose the nickel compound to the oxide or elemental metal.

One preferred method for forming the initial composite of the nickelcomponent with the carrier includes treating an inorganic oxideparticles with an aqueous solution of a soluble nickel compound. Generally, the inorganic oxide particles utilized will have been basic agedand water washed. For example, the inorganic gel particles may comprisespheroidal particles of uniform physical characteristics formed bydispersing an inorganic oxide hydrosol in the form of droplets into asuitable gelling medium and immediately thereafter subjecting theresulting gel spheres to an aging treatment in a basic medium. Thegelling medium may be any suitable water immiscible suspending liquid,usually a light gas oil chosen principally for its high interfacialtension with respect to water. Basic aging is usually accomplished byinitially commingling a weak base such as urea, hexamethylenetetramine,or the like, with the hydrosol before dispersing the same in the gellingmedium as described above. During the subsequent aging process, the weakbase retained in each gel particle continues to hydrolize, formingammonia and carbon dioxide. Generally, the spheres are retained in thegelling medium at a temperature of 120F. to 2l0F. in a separate vesselto complete the aging process. The aging process usually furthercomprises an aqueous ammonia treatment before a final water wash toremove soluble matter. The basic aged, water washed, spherical gelparticles, with extraneous water decanted or filtered therefrom, arethen calcined at about 400C., usually in an air atmosphere, andsubsequently further treated with a solution of a soluble compound ofnickel such as nickel nitrate, nickel sulfate, nickel chloride, ornickel acetate. The particles are soaked in the water-soluble nickelcompound solution for about 1 to about 2 hours at room temperature andthereafter evaporated by dryness in, for example, a rotary steam dryer.The dried composite is then heated at about 100C. to about 300C. for lto 2 hours. If the heating is performed in an air atmosphere, theresulting initial composite of nickel component and carrier materialwill contain nickel in the form of the oxide.

Another preferred method of preparing the initial composite of thenickel component with the carrier, when the carrier material iskieselguhr or the like, is by adding a hot aqueous solution containingthe required amount of nickel sulfate or nitrate to a suspension ofkieselguhr in water and subsequently heating the resultant mixture at atemperature of about 60 to about 80C. while a hot aqueous solution ofsodium carbonate is added thereto with stirring to precipitate nickelcarbonate and upon the kieselguhr. Thisprecipitation is usually carriedout at a temperature of about 60 to about 80C. and particularly goodresults are obtained at about 70C. It has been found desirable to addabout 1.7 molar proportions of sodium carbonate per atomic portion oftotal nickel ions in order that the finished catalyst will have thedesired consistency. The mixture of nickel carbonate and kieselguhr maythen be separated from the aqueous solution by filtration. The solidmaterial is dried, mixed with about 4 percent by weight offinely-divided graphite to act as a pelleting lubricant and formed intopellets by, for example, a pilling machine. The pelleted material maythen be heated in air at about 300 to about 400C. to decompose thenickel carbonate into nickel oxide. After the evolution of carbondioxide has substantially ceased, the resultant mixture of nickel oxideand kieselguhr may be utilized directly as the initial composite, or thenickel may be converted to the elemental metal by heating the compositein a stream of hydrogen at a temperature up to about 550C.

The next essential step in producing the catalytic composition, afterthe formation of the initial composite of the nickel component with thecarrier material, is sulfiding of the composite to produce a sulfidedcomposite containing at least about 0.9 mole of sulfur per mole ofnickel, i.e., the initial composite is subjected to sulfiding conditionssufficient to provide the sulfided composite with a sulfur/nickel atomicratio of about 0.9 or more. The initial composite is sulfided bycontacting it with a sulfide-yielding compound at sulfiding conditions.The sulfide-yielding compound utilized in this step may be any inorganicor organic sulfide-containing compound capable of producing nickelsulfide when contacted with the initial composite of the nickelcomponent and carrier material at sulfiding conditions. One suitablesulfide-yielding compound is hydrogen sulfide. Ammonium sulfide,ammonium hydrosulfide, the alkyl and aryl mercaptans, organic andinorganic soluble sulfides and organic thioethers, disulfides,thioaldehydes, thioketones and the like sulfur-containing compounds mayalso be employed, although not necessarily with equivalent results.Although the sulfiding step may in some cases be performed under liquidphase conditions, the preferred procedure involves contacting a gasstream containing the sulfide-yielding compound with the initialcomposite. Accordingly, the sulfide-yielding compounds which are morepreferred are volatile at the hereinafter specified sulfidingconditions. In general, best results in the sulfiding step have beenobtained when the sulfide-yielding compound is hydrogen sulfide insolution in a major portion of hydrogen. The sulfiding conditionsutilized are selected to produce a reaction between the nickel componentof the initial composite and the sulfur-containing sulfiding material inorder to form a nickel sulfide-containing composite. Ordinarily,temperatures ranging from about 10C. up to about 550C. or more areoperative, with the preferred temperatures being about 20C. to about450C. when hydrogen sulfide is utilized. The temperature employed mayvary, depending on the strength of the sulfiding agent, etc. Thepressure utilized can be selected from an extremely broad range and doesnot greatly effect the course of the sulfiding step. Ordinarily,atmospheric or subatmospheric pressures can be utilized with goodresults. It is ordinarily preferred to continue the sulfiding operationuntil the composite no longer reacts with the sulfide-yielding compound.

A preferred method for sulfiding the initial composite is by passing amixture of hydrogen sulfide and hydrogen over the initial composite.Good results are obtained when the amount of hydrogen sulfide is betweenabout 5 percent and about 30 percent of the hydrogen in the mixture. Thetemperature maintained during the preferred sulfiding operation is about20C. to about 450C. The gaseous hydrogen sulfide-hydrogen mixture ispreferably passed over the composite at the rate of about 250 cc. toabout 1,000 cc. per minute per cc. of composite. The sulfiding operationis continued until the amount of sulfur in the composite, in the form ofthe sulfide, is at least about 0.9 mole of sulfur per mole of nickel inthe composite and preferably about 1 mole or more of sulfur per mole ofnickel. Excess hydrogen sulfide is then purged from the sulfidedcomposite.

The third essential step in producing the catalytic composite of thepresent invention, after the formation of the initial composite of thenickel component and the porous carrier and sulfiding of the initialcomposite, is the removal of a critical amount of sulfur from thesulfided composite by stripping the sulfided composite with ahydrogen-containing gas at stripping conditions to provide the catalystutilized in the present isomerization operation. The gas utilized in thestripping operation may be pure hydrogen or may be a mixture of hydrogenwith gases substantially inert in the stripping operation such asnitrogen, argon, etc. Pure hydrogen gas is preferred for use. Thestripping operation generally includes continuously passing thehydrogencontaining gas over the sulfided composite, but may also beconducted in a batch-type operation in which a quantity ofhydrogen-containing gas is contacted with the particular quantity ofsulfided composite to be stripped for a specified period of time at thedesired temperature and pressure, and the gas is subsequently purged orotherwise removed from contact with the stripped composite. In such abatch-type operation, a large number of repetitions of the operationwill generally be required. A continuous stripping operation ispreferred because of its obviously greater ease of operation and morerapid results in stripping the desired amount of sulfur from thesulfided composite to form the desired catalyst composition. Thecontinuous operation includes continuously passing a stream ofhydrogen-containing gas, preferably pure hydrogen, over the sulfidedcomposite. The stripping operation can be performed in a fairly broadtemperature range, e.g., about 200C. to about 600C. or more. In order todetermine the amount of sulfur stripped from the sulfided composite, theamount of the sulfur in the sulfided composite can be determined byanalysis before commencing the stripping operation. The strippingoperation is then started and continued, with the amount of sulfurremoved being continuously determined by analysis of thehydrogen-containing gas stream after it is passed over the sulfidedcomposite. Preferably, the hydrogencontaining gas is passed over thesulfided composite at the rate of about 250 cc. to about 2,000 cc. perminute of hydrogen per 100 cc. of the sulfided composite. Preferably atemperature of about 300C. to about 600C. or more is maintained duringthe stripping operation, with a temperature of about 400C. to about600C. especially preferred. At stripping temperatures higher than 600C.the porous carrier material employed in the composite may sufferdeleterious results, especially from prolonged stripping operations.Generally, the amount of sulfur which can be stripped away from thesulfided composite is relatively small. It is very difficult to stripenough sulfur from the sulfided composite to provide a final catalysthaving less than about 0.7 mole of sulfur per mole of nickel. The timeand temperatures involved in stripping enough sulfur from the compositeto obtain a final sulfur/nickel mole ratio less than 0.55 substantiallyprohibit forming a final catalyst having such a composition. Sinceexcellent results can be obtained using a catalyst having sulfur/nickelmole ratios as high as 0.8 to 0.9, the preferred ratio is about 0.6 toabout 0.9. After the desired amount of sulfur has been stripped from thesulfided composite so that less than 0.9 mole and greater than 0.55 moleof sulfur remains in the composite per mole of nickel in the composite,calculated as the elemental metal, the stripping operation isdiscontinued and the final catalytic composite is then ready for use inthe isomerization operation of the present invention. The nickel in thefinished catalyst should be present in a catalytically effective amount,generally about wt. percent to about wt. percent of the finishedcatalyst. A preferred range of nickel content in the finished catalystis about 10 wt. percent to about 60 wt. percent.

The catalyst of the present invention can in general be employed in theisomerization of the olefinic double bond of a variety of olefins.Olefins which may be isomerized using the process of the presentinvention include generally all mono-olefins in which the olefinic bondis shiftable to convert the olefin to a different isomeric olefin.Specific isomerizable olefins include butene-1, butene-2, methylbutenesand n-pentenes, hexenes, decenes, etc. The present process producesessentially equilibrium conversion of an isomerizable reactant olefin.For example, use of a particular butene or pentene isomer as thereactant olefin in the present process will convert the reactant olefinto an equilibrium mixture of butene double bond isomers or pentenedouble bond isomers, respectively.

The preferred olefins for use in the present isomerization process arebutenes. It is well known in the art that butene-l is only available ona commercial scale commingled with at least some isobutylene. This isprimarily because of the similar boiling point of butene-l andisobutylene, which render there separation by fractionation infeasible.The commercial operations which are the only available source of Colefins, e.g., fluid catalytic cracking and thermal cracking operations,provide butene-l and butene-2 supplies whichcontain at least about 10-20percent isobutylene, while the amount of isobutylene in the C olefinsupplies produced in these operations is often as high as 5060 percentof the C olefins content. Butene-2, which is more valuable as a chemicalprecursor than butene- 1, can be separated from the other two C olefinisomers by fractionation, so that by isomerizing the butene-l fractionit is then possible to recover substantially all the linear C olefins asbutene-2 by fractionating the C olefins to separate butene-2 fromisobutylene and butene-1. The isobutylene and butene-l can be recycledto the isomerization operation so that substantially all of the butene-lcan be converted to butene-2 and subsequently separated from theisobutylene. In such an operation, a drag stream containing a highconcentration of isobutylene must be removed from the recycle stream ofbutene-l and isobutylene in order to prevent a buildup of isobutylene inthe operation.

An olefin to be isomerized in the process of the present invention maybe utilized in the form of a pure compound or may be admixed with otherolefins, saturated hydrocarbons, aromatics, etc., or any other materialwhich is relatively inert at the isomerization conditions employed.Commercially available olefin feed stocks generally contain the reactantolefin in admixture with at least one saturated hydrocarbon, since, inorder to recover all the reactant olefin from a particular source, atleast some saturated hydrocarbons are also necessarily recovered becauseof imprecise fractionation and economic limitations. Suchsaturate-diluted feed stocks are generally preferred for use in thepresent process. For example, commercial sources of butene-l generallysupply the butene-l in admixture with saturated hydrocarbons such aspropane, isobutane, etc. The primary commercial sources of butene-l arecatalytic and thermal petroleum cracking operations. A typical butene-lfeed stock supplied to the present isomerization process from such acracking operation might contain 30-70 vol.% isobutane and/or propane.Sucha feed stock is suitable for use in the present process. Asdescribed above, isobutylene is almost invariably present incommercially available supplies of butene-l. For example, a typicalfluid catalytic cracking operation might supply a butene-l feed stocksuitable for use in the present process which contains vol. percentpropane, vol. percent butene- 1 vol. percent butene- 2, 25 vol. percentisobutylene, and 45 vol. percent isobutane. It is apparent from thisexample that a process for isomerizing the butene-l component of such afeed stock must be selective for the desired double bond isomerizationreaction, and inert to other hydrocarbons.

Olefin isomerization conditions useful in the process of the presentinvention include a temperature of about 25C. to about 200C. Thepreferred temperature range is from about 75C. to about 160C. Althoughisomerization can be effected when the present process is performedusing liquid phase operations, it has been found that the catalyst ofthe present invention deactivates fairly rapidly unless vapor phaseoperations are maintained. Thus, the pressure preferred in the presentprocess is that chosen to provide vapor phase operations at theparticular temperature desired for use. In general, a pressure ofsubatmospheric to about 30 atmospheres is satisfactory. Normally theoperations should be conducted with the temperatures and pressure abovethe dew point of the least volatile component of the olefin-containingfeed stock employed in the process. The reaction times utilized in thepresent process are preferably calculated, in general, on the basis ofthe volume of olefinically unsaturated hydrocarbons (excludingpropylene) which are contacted with the catalyst. For example, using afeed stock containing propane, butene-l isobutylene, butadiene andisobutane, the reaction time is preferably calculated on the basis ofthe volume of combined butenel, isobutylene and butadiene employed. In apreferred, continuous operation, this space velocity is referred to asthe olefin space velocity," which is intended to describe the spacevelocity of all C, and heavier olefinically unsaturated hydrocarbons inthe feed stock employed, irrespective of the exact amounts of saturates,hydrogen, etc., which are utilized. Thus, in the preferred continuousoperation, an olefin liquid hourly space velocity (liquid volume of C,and heavier olefins per hour per volume of catalyst employed) of about0.5 to about may suitably be employed. An olefin liquid hourly spacevelocity of about 1 to about 10 is preferred. At lower space velocities,a lower temperature may generally be employed. The space velocity andtemperature and normally adjusted according to the content of the feedstock to give high conversions at the highest possible space velocitywith vapor phase operations. Some hydrogen is required in the operationfor satisfactory performance. At least-about 0.01 mole of hydrogenshould be charged to the isomerization operation for every mole ofunsaturates charged, and preferably about 0.1 mole of hydrogen isadmixed with each mole of feed stock. More hydrogen may be required whenlarge amounts of sulfur and/or polyolefins such as butadiene are presentin the olefin feed stock employed. One significant advantage of thepresent process is that the isomerization operation is not adverselyeffected by fairly high water levels in the feed stocks employed. Forexample, a water level of 200 ppm. in the feed has substantially. noeffect on the operation.

The isomerization process of the present invention may be performedusing any suitable reactor known to the art. A batch-type operation maybe employed, in which a fixed portion of olefin-containing feed stockand a specific amount of the catalyst of the present invention areplaced in an appropriate vessel, such as an autoclave, and contactedtherein for an appropriate length of time. The isomerized charge stockis then withdrawn from the vessel and the isomerized olefin isrecovered. The preferred mode of operation is a continuous-typeoperation. The catalyst may be utilized as a fixed bed, with thehydrocarbon charge stock continuously being passed over the bed. Thecatalyst may also be employed in a moving bed operation including bothcountercurrent and co-current operations. The preferred mode ofoperation is a continuous fixed bed operation in which the reactantolefin is continuously passed into the reactor and downwardly over afixed bed of the catalyst and then withdrawn continuously from thereactor. A large variety of conventional reactors suitable for use inthe present process will be obvious to those skilled in the art from theforegoing.

EXAMPLE I An initial composite of nickel and kieselguhr was prepared bysuspending kieselguhr in an aqueous solution of nickel nitratecontaining a calculated amount of nickel to give a nickel-kieselguhrcomposite containing 50 wt. percent nickel. The mixture of nickelnitrate solution and kieselguhr was heated to C., precipitated withsodium carbonate, filtered, washed, dried, pilled and heated at 300400C.to decompose nickel carbonate to nickel oxide. The oxide was thenreduced in a stream of hydrogen at 400C. to reduce the nickel to theelemental metal form. The composite was then analyzed and found tocontain 50 wt. percent nickel, as the elemental metal, and 50 wt.percent kieselguhr. This composition was designated Catalyst A.

EXAMPLE II A 1,000 cc. sample of Catalyst A was sulfided by passing overit a stream of hydrogen containing 10 percent hydrogen sulfide andmaintained at 400C. until no further hydrogen sulfide was found to reactwith the composite. This sulfided composite was analyzed and found tohave a sulfur/nickel mole ratio of 1.1. This composite was designatedCatalyst B.

EXAMPLE III A cc. sample of Catalyst B was stripped by passing a streamof hydrogen over it at the rate of 1,000 cc. per minute at a temperatureof 300C. for 4 hours. This catalytic composite was analyzed and found tohave a sulfur/nickel mole ratio of 1.0. it was designated Catalyst C.

EXAMPLE IV Another 100 cc. sample of Catalyst B was obtained andstripped by passing 1,000 cc. per minute of hydrogen over it at 400C.for 4 hours. Analysis of the stripped composite showed it to have asulfur/nickel mole ratio of 0.89. This composite, prepared inconformance with the present invention, was designated Catalyst D.

EXAMPLE V Another 100 cc. sample of Catalyst B was stripped by treatingit with a stream of 1,000 cc. per minute of hydrogen at a temperature of500C. for 4 hours. Analysis showed the sulfur/nickel mole ratio of thiscomposite, prepared in accordance with the present invention, to be0.85. This composite was designated Catalyst E.

EXAMPLE VI A further 100 cc. sample of Catalyst B was stripped bypassing 1,000 cc. per minute of hydrogen over it at sulfide with thecomposite was observed. This sulfided EXAMPLE XII a temperature of 600Cfor 4 hours. Analysis of the resuiting sulfided and stripped composite,prepared acu A through H we re comPared m P phase cording to the presentinvention, showed it to have a lsomenzauon of bmene'l m adm'xture withlsobutyl' sulfur/nickel mole ratio of 0.76. This composite was In Fexactly the S,ame amount of catalyst was used in the same conventionalreactor. The feeddeslgnated Catalyst 15 stock employed contained 55 60mole percent pro EXAMPLE Vll pane diluent and 2:1 butene-l/isobutylenevolume ra- A conventional spherical alumina base was impregamoupt ofhydrogen used was that wh'qh nated with a solution of sufficient nickelnitrate to prowould dissolve m shydmcarbin feedstock at duce a calcinedand reduced composite containing 25 i temperature an g ffg pressgre' wt.percent nickel. The dried composite was heated to zi l i a t 9mg? e300C. to decompose the nitrate and form nickel oxide. f i g 5" y sfiaceThe nickel was then reduced to the elemental metal by 2:31 2 a c targepassing a stream of hydrogen over the composite at p u 0 ca ys O anempera i 0 o 100C, and the temperature was ad usted to provide a l 400C. The resulting composite of 25 wt. percent e e 25 f 70 80 G ntalnickel on alumina was designated Catalyst G conversion perceml 6mm aparticular men run was terminated if conversion was low at 140C. InEXAMPLE v1 each case, the effluent from the reactor was analyzed. A 500cc. sample of Catalyst G was sulfided by pass- The results are shown mTable ing over it a stream of hydrogen containing 10 percent EXAMPLEXIII hy'dmgen A temperature of 9 was i Catalysts D, I, J and K werecompared under exactly tamed qurmg the Sulfidmg step Sulfidmg was thesame conditions employed in the runs described in until no furtheruptake of hydrogen Sulfide h Example XII except that the feedstockcontained 0.2 catalyst was observed. The sulfur/nickel mole ratio inmole percent l,3 butadiene and hydroggn was charged this comp ysulfiqfid nlckeljalumma Q p was with the hydrocarbons at the rate of 1liter per hour per g to be Thls composlte was designated Cata' l0 cc. ofcatalyst. The results are shown in Table II. y Referring to Table I, thesurprising activity and stabil- EXAMPLE IX of the catalystconzgositlions lp)relrgarecrii lafcording to e present invention ataysts an are appar- A 100 Sample Of Catalyst H PP by P 40 cut. Forexample, Catalyst D, after 660 hours of continconversion ac reve y any 0t e compositions, an lyzed and found to have a su C e ratio of this highlevel of conversion was maintained with only 0. h comp i p p accordingto the P a 2C. temperature. rise in 600 hours. Catalysts E and cutinvention, as des gnatd Catalyst F also attained very high conversionrates which were particularly desirable because of the relatively lowtem- EXAMPLE X peratures at which these catalysts exhibited stable ac-Another 100 cc. sample of Catalyst H was stripped in tivity. Incontrast, Catalyst A (elemental nickel) was tream of h dro en at 1,000cc. er minute and a found to be unstable and also relat' l l a t' 't ier nperature o f 605C. for 4 hours. The resulting sul- The sulfidednickel catalysts, B ziiid C? i ve r e aliiibgt fided and strippedcomposite, prepared in accordance completely inactive. The very lowactivity of Catalyst with the present invention, was analyzed and foundto C is particularly significant in that it illustrates the critihave asulfur/nickel mole ratio of 0.57. This composite cal nature of thesulfur/nickel mole ratio in the catalyst. was designated Catalyst .1.Merely stripping some sulfur from a completely sulfided composite (suchas Catalyst B) is not sufficient, EXAMPLE XI as shown by the lowactivity of Catal st C. Yet when y A 100 cc. sample of Catalyst G (25percent elemensufficient sulfur is stripped to provide a catalyst with atal nickel on alumina) was treated with a stream of hysulfuf/mckel lratio below about (Catalyst drogen containing IOpercent hydrogen sulfideat ambiacmlty stablllty ent temperature until no further reaction ofhydrogen RfiQfl'PgjQ T me" l l P i}? F TABLE I Catalyst A B c D E F o HSulfur/Nickel ratio 0 1.1 L0 0.89 0.85 0.76 0 0.95 Hrs. in use 270 20 2060 660 140 so 20 35 l5 Reactor Temp. C. 140 140 I40 143 I45 123 I30ABLE. C9ntinne Catalyst B C D E F G H uimrmmms in Product (Mule a oft]!(Feed) isobutylene 3245 33.2 33.9 33.5 33.4 33.6 32.5 32.5 32.7 33.032.9 34.0 hUIQIlE l 65-68 19.6 14.8 59.0 46.6 16.4 10.8 12.7 12.9 34,046.1 59.0 butene-2 47.2 51.2 7.5 20.0 50.0 56.7 54.8 54.4 33,0 21.0 7.0

'72 Conversion (Mole "/1 butene-2/Mole "/1 butene-l and butene-Z) 70.677.6 11.3 30.0 75.3 84.0 81.2 80.8 51.5 31.3 10.6

TABLE I1 alyst being prepared by the steps of:

a. forming an initial composite of said nickel compo- Catalyst 0 l J Knent and said carrier material, said nickel component being present inthe initial composite as the fiulfur/Nickel Ratio 0.89 0.69 0.57 0.18elemental metal or the oxide;

rs. in use 1000 140 160 55 Reactor Temp 24 128 I26 98 b. sulfiding saidinitial composite by contacting same 1;, Components with asulfide-yielding compound at sulfidmg con- "g z g C S ditions to providea sulfided composite containing at least about 0.9 mole of sulfur permole of said (Feed) nickel component in the sulfided composite; and,n-butane 0.0 0.0 0.0 0.0 [.3 isobutylene 32.8 32.6 32.2 32.5 31.9 g 3-853 5 c. stripping sulfur from the resulting, sulfided comutenei r l 3bumdiene 02 0'0 0'0 0'0 00 pos1t e w1th a hydrogen-containing gas atstnppmg conditions to provide said olefin isomerizauon cat- I 8 gf' f'30 alyst, sufficlent sulfur being stripped from said sulo v, b n fidedcomposite to provide a sulfur content in said and Wale-2) 813 catalystof less than about 0.9 mole and more than about 0.55 mole of sulfur ermole of said nickel prepared accordmg to the present 1nvent1on(Catalysts component in the catalyst p ,lan a alof'sme" v D d J) re capb e l 0 butene 1 at cry 2. A catalyst according to cla1m 1 wherein saidcarhigh activity and excellent stability and selectivity, whilehydrogenating butadiene. Catalyst K, prepared with a sulfur/nickel moleratio below the level of the catalysts of the present invention, wasfound to hydrogenate the linear butenes to form substantial amounts ofn-butane, even when operated at low temperatures, i.e., Catalyst K wasfound to lack selectivity. Catalyst K was, therefore, inferior as anisomerization catalyst, since hydrogenation to n-butane is a veryundesirable side reaction in such an operation.

We claim as our invention:

1. A catalyst combination of a sulfur component and a catalyticallyeffective amount of a nickel component with a porous carrier material,said catalyst containing less than about 0.9 mole and more than about0.55 mole of said sulfur component per mole of said nickel mnqneps 92213912433 $1 9 e e ental ineta t id ca rier material is alumina.

3. A catalyst according to claim 1 wherein said carrier material issilica.

4. A catalyst according to claim 1 wherein said car- 40 rier material iskieselguhr.

' 5. A catalyst according to claim 1 wherein the catalyst contains about10 to about 60 wt. percent nickel, calculated as the elemental metal.

6. A method for preparing the catalyst composition defined in claim 1which comprises the steps of:

a. forming an initial composite of said nickel component and saidcarrier material, said nickel component being present in the initialcomposite as the elemental metal or the oxide;

. sulfiding said initial composite by contacting same with asulfide-yielding compound at sulfiding conditions to provide a sulfidedcomposite containing at least about 0.9 mole of sulfur per mole of saidnickel component in the sulfided composite; and,

. stripping sulfur from the resulting, sulfided composite with ahydrogen-containing gas at stripping conditions to provide said olefinisomerization catalyst, sufficient sulfur being stripped from saidsulfided composite to provide a sulfur content in said catalyst of lessthan about 0.9 mole and greater than about 0.55 mole of sulfur per moleof said nickel component in the catalyst.

2. A catalyst according to claim 1 wherein said carrier material isalumina.
 3. A catalyst according to claim 1 wherein said carriermaterial is silica.
 4. A catalyst according to claim 1 wherein saidcarrier material is kieselguhr.
 5. A catalyst according to claim 1wherein the catalyst contains about 10 to about 60 wt. percent nickel,calculated as the elemental metal.
 6. A method for preparing thecatalyst composition defined in claim 1 which comprises the steps of: a.forming an initial composite of said nickel component and said carriermaterial, said nickel component being present in the initial compositeas the elemental metal or the oxide; b. sulfiding said initial compositeby contacting same with a sulfide-yielding compound at sulfidingconditions to provide a sulfided composite containing at least about 0.9mole of sulfur per mole of said nickel component in the sulfidedcomposite; and, c. stripping sulfur from the resulting, sulfidedcomposite with a hydrogen-containing gas at stripping conditions toprovide said olefin isomerization catalyst, sufficient sulfur beingstripped from said sulfided composite to provide a sulfur content insaid catalyst of less than about 0.9 mole and greater than about 0.55mole of sulfur per mole of said nickel component in the catalyst.